L4 - Introduction to Simulation

Question 1

What is a simulation?

Answer 1

• Many similar definitions of simulation, but essentially, simulation is an imitation of reality
• Experiment with model of real (but not necessarily existing) situation in order to increase understanding and/or enhance the real situation
• Assume model is sufficiently “real” to tell us something about reality

Question 2

When is simulation applicable?

Answer 2

1. Variability - Predictability and unpredictability –> you dont know some things so it helpful to simulation different scenarios
2. Interconnectedness - Eariler stages affect later stages
3. Complexity - Problem is difficult e.g many combinations

Question 3

What is a deterministic and a stochastic demand model?

Answer 3

Deterministic demand model is a model where the parameter of the model can be obtained without any ambiguity while the parameters of a stochastic model are controlled by a probability distribution function.

Question 4

What should random numbers be?

Answer 4

• Random numbers should be:
• Random – numbers should be in random sequence
• Evenly distributed – each of the 100 numbers should have same chance of occurring
• Independent – if number appears, then chance of appearing again is unaffected

Question 5

Top hat method?

Answer 5

Used to manually generate random numbers
Take 100 pieces of paper
Write values 00, 01, 02, …, 99 (even distribution)
Place pieces of paper in hat
Shake hat to mix numbers (random distribution)
Pull out piece of paper and note number
Place paper back in hat (independent)
Repeat from step 4

Question 6

How can you simulate variable demand?

Answer 6

• write out the daily demand and its percentage of occurance, in order
• add up the percentages cumulatively
• starting at 00 up to the number just before the the cumulative percentage, write the corresponding random number for each daily demand
• no by generating random numbers for different days you can simulate random daily demand